riscv64: pointer-width load/store

Match load/store widths to the data fields being accessed.

Test: Run ART test 001-HelloWorld on a Linux RISC-V VM:
  lunch aosp_riscv64-userdebug

  export ART_TEST_SSH_USER=ubuntu
  export ART_TEST_SSH_HOST=localhost
  export ART_TEST_SSH_PORT=10001
  export ART_TEST_ON_VM=true

  . art/tools/buildbot-utils.sh
  art/tools/buildbot-build.sh --target

  # Create, boot and configure the VM.
  art/tools/buildbot-vm.sh create
  art/tools/buildbot-vm.sh boot
  art/tools/buildbot-vm.sh setup-ssh  # password: 'ubuntu'

  art/tools/buildbot-cleanup-device.sh
  art/tools/buildbot-setup-device.sh
  art/tools/buildbot-sync.sh

  # Test Nterp (first revert https://r.android.com/2547153 in local build)
  art/test.py --target -r --no-prebuild --ndebug --64 001-HelloWorld
  # SIGILL in nterp_op_new_array

Change-Id: I8fe2c81f7cb1d4c3793e00e424da2310b55903e9
diff --git a/runtime/interpreter/mterp/riscv64/main.S b/runtime/interpreter/mterp/riscv64/main.S
index e1f8a72..15033bf 100644
--- a/runtime/interpreter/mterp/riscv64/main.S
+++ b/runtime/interpreter/mterp/riscv64/main.S
@@ -100,7 +100,7 @@
     SETUP_SAVE_REFS_ONLY_FRAME
     call \helper
     RESTORE_SAVE_REFS_ONLY_FRAME
-    lw t0, THREAD_EXCEPTION_OFFSET(xSELF)
+    ld t0, THREAD_EXCEPTION_OFFSET(xSELF)
     bnez t0, nterp_deliver_pending_exception
     ret
 END \name
@@ -177,7 +177,7 @@
     mv \old_sp, sp
     .cfi_def_cfa_register \old_sp
     mv sp, t0
-    sw \old_sp, -8(\refs)
+    sd \old_sp, -8(\refs)
     CFI_DEF_CFA_BREG_PLUS_UCONST \cfi_refs, -8, FRAME_SIZE_SAVE_ALL_CALLEE_SAVES
 
     // Put nulls in reference array.